Which liquid pesticide formulation contains solid particles that do not dissolve in either water or oil?

The correct answer is flowables. Flowables are a type of pesticide formulation that consists of solid pesticide particles suspended in a liquid carrier, such as water or oil. These solid particles do not dissolve; instead, they remain in suspension, allowing the product to be spread evenly during application. This formulation is particularly useful for active ingredients that might otherwise be difficult to use due to their low solubility in conventional liquid carriers.

In contrast, emulsifiable concentrates involve a formulation where the active ingredient is dissolved in oil and can create a stable emulsion when mixed with water. Water-soluble powders are designed to dissolve in water completely, forming a solution. Liquid concentrates typically refer to concentrated solutions that may or may not contain dissolved solids, but they are fundamentally different from flowables in that they do not have the characteristic solid particles suspended in the liquid. Thus, flowables are the unique formulation among the options that fits the description of solid particles that do not dissolve in either water or oil.